setParams above is the thing that sets all the curve info. I was incorrect in my original post, you only need to set the params for the public key. In this case I was generating a 256 bit key pair - (NIST P-256 curve) so the keylen parameter in buildKey was '256'.

This works for my J3A JCOP card.

You may want to go back and re-confirm your curve parameters, there are combinations that give illegal results.